1. Field of the Invention
The present invention relates to a CMOS power amplifier applicable to a front end module and, more particularly, to a CMOS power amplifier that can be selectively used as a non-linear amplifier or a linear amplifier by regulating an amplification gain thereof.
2. Description of the Related Art
In general, nearly 80% or more of the demand for mobile phones worldwide re for GSM (Global System for Mobile communication) phones using a non-linear signal, and EDGE or W-CDMA phones using a linear signal are anticipated to be widely preferred and used in the future market.
Thus, an amplifier that is able to selectively amplify a GSM signal and an EDGE/W-CDMA signal, as a single power amplifier, is required.
The related art power amplifier is classified into a non-linear amplifier that can amplify a non-linear signal such as a GSM signal and a linear amplifier chat can amplify a linear signal such as an EDGE/W-CDMA signal, and the like.
The operation principle of the non-linear amplifier is as follows. In the case of a GSM signal without information in an envelope thereof, an amplifier having a large gain is used in order to convert a changing envelope of an input signal into a uniform envelope.
The operation principle of the linear amplifier is as follows. In the case of an EDGE/W-CDMA signal having information in an envelope thereof, an amplifier must amplify an input signal such that it maintains a signal form with a uniform gain.
However, as for the related art power amplifier, a non-linear amplifier is required in order to amplify the non-linear signal such as the GSM signal or the like, and a linear amplifier is required in order to amplify the linear signal such as the EDGE/W-CDMA signal, and the like. Namely, in order to amplify the different signals, two different amplifiers must be purchased.